DDTexlaxed
TRANSITION OVER! 11-22-14
You're not going to lose your hair. I had a henna mishap that was much worse. I mixed it with apple juice and a little lemon juice, clarified my hair and applied it overnight. The next day when I washed it out, my hair was completely stripped. I panicked big time and posted a thread about it back in 2008. My hair was so fragile I was afraid to touch it. But with time, and lots of TLC, it completely recovered and regained its moisture. I didn't even have a setback.
Like others suggested, I would also recommend that you read through one of the henna threads and work on your plan of attack. The color is easily fixable, and the dryness will improve with some deep conditioning. Also make sure that you got all of the henna out. It usually takes me several poos and condishes to get it all.
I no longer have dry hair issues, just very soft touchable hair now.

